By "what they would be like", I'm not thinking of lifestyle, opinions, beliefs, or any of the things that can be affected by circumstances and/or the influence others may have had on any of them - just general nature, as a person. I think it was pretty clear certainly by the time each was four years old, but in many ways when they were three years old. In a very limited few ways, before reaching their second or even first birthday.
Since all three are over thirty now I won't go into details in the interest of their grown-up privacy; but while I couldn't have seen, at the time, the ways in which all three would "still be the same" I could today write a list of all the ways in which each is the same today as s/he was a young child or even baby.
Then, too, all three were the same in x number of ways while each was different in some limited x-number of ways too.